Insulin Overdose

Insulin overdose causes severe, prolonged hypoglycemia by increasing glucose uptake and suppressing hepatic glucose production. It occurs from dosing errors, deliberate self-harm, accidental pediatric exposure and factitious use. Most patients are people with diabetes or healthcare workers with access, and the condition also appears in homicidal and Munchausen presentations.

Duration of action depends on the preparation and route:

• Intravenous regular insulin: 2 to 4 hours
• Subcutaneous rapid-acting analogues: 4 to 6 hours
• Neutral protamine Hagedorn: 12 to 24 hours
• Long-acting analogues (glargine, detemir, degludec): 24 to over 96 hours
• Massive subcutaneous overdose: a depot effect that delays absorption for several days

Complications: neuroglycopenic brain injury, seizures, cardiac arrhythmia and myocardial ischemia, hypokalemia, hypophosphatemia, hypomagnesemia, aspiration and death. Prolonged coma carries a risk of permanent cognitive damage.

• Adrenergic features: sweating, tremor, palpitations, tachycardia, anxiety, hunger
• Neuroglycopenic features: confusion, slurred speech, personality change, visual disturbance, seizures, focal deficits, coma
• Hypokalemia with weakness, arrhythmia and ileus
• Unexplained recurrent hypoglycemia in a person without diabetes
• Red flags: coma, seizures, persistent hypoglycemia beyond 12 hours, glucose under 2.0 mmol/L and ingestion of long-acting insulin

1. Capillary and laboratory glucose, hourly during treatment.
2. Investigation of unexplained hypoglycemia (before dextrose if possible): insulin, C-peptide, proinsulin, beta-hydroxybutyrate, sulfonylurea screen. Exogenous insulin gives high insulin, suppressed C-peptide and proinsulin. Insulinoma and sulfonylurea give high C-peptide.
3. Electrolytes (potassium, phosphate, magnesium), creatinine, blood gases, lactate.
4. ECG, and a physical examination for injection sites, including a search for sites with a palpable depot.
5. Paracetamol and salicylate levels in suspected self-harm.

Differentials: sulfonylurea poisoning, insulinoma, adrenal insufficiency, sepsis, liver failure, alcohol-related hypoglycemia, starvation, other drugs.

1. Immediate glucose: 50% dextrose 25 to 50 mL IV (children 10% dextrose 2 to 5 mL/kg) for symptomatic hypoglycemia, or oral glucose 15 to 20 g if alert.
2. Continuous infusion: 10% dextrose at 100 to 150 mL/h (children 5 mL/kg/h), titrated to glucose of 5 to 10 mmol/L. Use 20% dextrose through a central line if fluid restriction is needed. Check glucose every 30 minutes initially and then hourly.
3. Glucagon 1 mg IM, SC or IV (children 0.5 mg, or 20 to 30 micrograms/kg) is an adjunct when IV access is delayed. It works only when hepatic glycogen is present, so it fails in starvation, alcohol use and liver disease, and effects last under an hour.
4. Potassium: replace to 3.5 to 4.5 mmol/L (potassium chloride 10 to 20 mmol IV over 1 to 2 hours with monitoring). Replace phosphate and magnesium (magnesium sulfate 2 g IV).
5. Surgical excision of the depot (a rare intervention) for massive subcutaneous overdose of long-acting insulin with persistent hypoglycemia over 24 hours, by removing the injection-site tissue with ultrasound or marking guidance.
6. Unconscious patient: protect the airway, and treat seizures after correcting glucose with lorazepam 4 mg IV (children 0.1 mg/kg).
7. Avoid octreotide unless the cause is sulfonylurea or the endogenous insulin is raised. It has no role in exogenous insulin overdose.
8. Observation: at least 4 to 6 hours after the last dextrose with normal glucose for short-acting insulin, and 24 hours or more for long-acting preparations and massive overdose.

Follow-up: psychiatric assessment for intentional overdose, review of insulin dosing technique, pen device and storage, and education on hypoglycemia. In suspected factitious or homicidal use, involve the appropriate authorities and safeguarding teams.